Image quality in CT scans of the heart may be affected by heart motion. Motion of the heart within the duration of a cardiac CT scan capture may result in the presence of motion artifacts in images derived from the cardiac CT scan.
FIG. 1 shows an image derived from a CT scan of the heart. Ellipses 2 indicate vessels with severe motion artifacts. Normally, in an image derived from a scan without significant motion artifacts, it may be expected that vessels would appear as approximately circular. However in FIG. 1 the vessels within ellipses 2 are significantly distorted.
Heart motion may particularly affect image quality in scans that are taken at high heart rates, for example heart rates over 60 beats per minute (bpm). Advanced scanners may obtain good image quality with moderately high heart rates, but may still see decreased quality at higher heart rates.
Scanners with a fast rotation may produce better results than scanners with a slower rotation, but motion artifacts may still be an issue even when fast rotation is used.
For some patients, drugs such as beta-blockers may be administered to slow the patient's heart rate, for example to slow the patient's heart rate below 60 beats per minute. However, beta-blockers may be contraindicated in some patients. Some patients may be unable to take beta-blockers, for example due to medical conditions.
It is known to estimate heart motion by comparing image data that is representative of different points in time, to determine motion that has occurred between the different time points.